DYNAMIC VOLTAGE RESTORER (DVR) FOR VOLTAGE SAG COMPENSATION WITH FUZZY LOGIC CONTROLLER. Chennai, Tamilnadu, India. Chennai, Tamilnadu, India.

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1 Volume 119 No , ISSN: (printed version); ISSN: (on-line version) url: ijpam.eu DYNAMIC VOLTAGE RESTORER (DVR) FOR VOLTAGE SAG COMPENSATION WITH FUZZY LOGIC CONTROLLER M.I.ANJU *1, S.SIVAKAMI 2, N.AMBIKA 3, R.NISHANTHINI 4, *1,2 Assistant Professor, New Prince Shri Bhavani College of Engineering and Technology, Chennai, Tamilnadu, India. 3,4 PG Scholar, New Prince Shri Bhavani College of Engineering and Technology, Chennai, Tamilnadu, India. * Abstract This paper presents design and simulation of Dynamic voltage restorer (DVR) using Fuzzy Logic Controller (FLC). It describes the problems of voltage sags and its severe impact on nonlinear loads (or) sensitive loads. DVR is a series connected device used for compensating the voltage sags in distribution system. The detection of sags is carried out with the help of dqo theory, whereas THD level is reduced and control of voltage source inverter is done with help of Fuzzy Logic Controller. The simulation was carried out with the help of SIMULINK & MATLAB and the results were found to be in accordance with theoretical values. Keywords: Dynamic voltage restorer (DVR), Fuzzy Logic Controller, dqo theory, voltage sag. 1. INTRODUCTION The term power quality is something that describes the quality of power; it is the quality of voltage rather than power (or) current. Power Quality problems encompass a wide range of disturbances such as voltage sags/swells, flicker, harmonics distortion, impulse transient, and interruptions [1]-[4].Because of the voltage deviation the electrical utility is not able to supply the pure sinusoidal voltage of required magnitude and frequency. Voltage sags can occur at any instant of time, with amplitudes ranging from 10 90% and a duration lasting for half a cycle to one minute.voltage swell, on the other hand, is defined as a swell is defined as an increase in rms voltage or current at the power frequency for durations from 0.5 cycles to 1 min. typical 133

2 magnitudes are between 1.1 and 1.8 up [5]. These voltage problems can be solved using a series connected custom power device called dynamic voltage restorer (DVR). The emphasis has been given for switching control strategy i.e, pulse width modulation techniques and their results are presented. The main function of a DVR is the protection of sensitive loads from voltage sags/swells coming from the network. The following steps are used to implement the DVR in injection mode [6]. Step 1: To find out whether there is any sag/swell in the source voltage. It is done by comparing the terminal source voltages with reference load voltages. The difference between the source voltages and reference load voltages is the required amount of voltage that has to be injected by the DVR. Step 2: To generate switching commands to the VSI in order to track the reference voltages (generated in step 1) using a suitable switching scheme such as PWM. Step 3: To filter out the harmonics that are present in the output of the voltage source inverter. Step 4: To inject the filtered output through the three single phase series isolation transformers present between the source and the load. Voltage Compensation 2. RESULT AND DISCUSSION The designed DVR is used to compensate sags of magnitude in the range (0.2p.u p.u). But in reality a DVR can compensate a maximum of 0.5pu. For the purpose of demonstration sag of magnitude 0.2p.u is considered. The VSI is implemented using Fuzzy Logic Controller and the result is carried out. 134

3 Figure.1. Sag Voltage Figure.2. Injected Voltage Figure.3. Compensated Voltage The first simulation show of three phase voltage sag is simulated. The simulation started with the supply voltage 20% sagging as shown in Figure.1.In Figure.1.also shows a20% voltage sag initiated at 0.2s and it is kept until 0.8s, with total voltage sag duration of 0.6s. Figures.2. and Figure.3.show the voltage injected by the DVR and the corresponding load voltage with compensation. As a result of DVR, the load voltage is kept at 1 p.u. Total Harmonics Reduction Figure.4. without controller THD waveform 135

4 Figure.5. with PI controller THD waveform Figure.6. with fuzzy logic controller THD waveform Reduction of Total Harmonics Distortion is reduced with help of fuzzy logic controller when compared to conventional controller; it is observed from figures 4, 5 and 6. CONCLUSION The modeling and simulation of DVR using MATLAB/SIMULINK has been presented. The performance of DVR is studied under voltage Sag and reduction of THD by using Fuzzy Logic Control Technique. From the simulation results DVR compensate the voltage Sag quickly and THD is reduced with fuzzy controller compare to conventional controller and provides better voltage regulation. 136

5 Reference [1] Design, Modelling and Simulation of Dynamic Voltage Restorer for Voltage Swell/Sag Mitigation. Journal of Engineering Science and Technology (IJEST). ISSN Vol. 3 No. 6 June [2] Design and Simulation of Dynamic Voltage Restorer (DVR) Using Sinusoidal Pulse Width Modulation (SPWM). Saripalli Rajesh, Mahesh K. Mishra, Senior Member IEEE and Sridhar. 16th national power systems conference, 15th-17th december, [3] Dynamic Voltage Restorer Based on Space Vector Pulse Width Modulation Technique. B.N S P Venkatesh* D.Prathap Hari Krishna, Gitam University. International Journal of Engineering Science and Technology (IJEST).ISSN : Vol. 3 No. 7 July [4] Modelling and Simulation For Voltage Sags/Swells Mitigation Using Dynamic Voltage Restorer (DVR). Rosli Omar and Nasrudin Abd Rahim Australasian Universities Power Engineering Conference (AUPEC'08). [5] Dynamic Voltage Restorer (DVR) for Voltage Sag Mitigation. Mahmoud A. El-Gammal1, Amr Y. Abou-Ghazala2, and Tarek EI-Shennawy3. International Journal on Electrical Engineering and Informatic-Vol 3, Number 1, [6]Matlab/Simulink Based Analysis Of Voltage Source Inverter With Space Vector Modulation.Auzanizidin, Tolesutikno. 137

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